Texas Instruments UCC38051D

Overview

UCC38051D from Texas Instruments is a transition-mode (boundary-conduction mode) power factor correction (PFC) controller in an 8-pin SOIC package, designed for low-to-medium power boost preregulators requiring IEC 61000-3-2 compliance. It integrates a transconductance error amplifier (90 µS typ), multiplier, zero-current detector, PWM logic, and ±750-mA peak gate driver, enabling single-stage PFC flyback converters for lighting and AC adapters.

For engineers reviewing the UCC38051D datasheet, UCC38051D pinout, UCC38051D application, or UCC38051D equivalent, this controller delivers precise 2.5-V internal reference, 12.5-V UVLO turn-on threshold, zero-power detect for light-load OVP prevention, slew-rate-enhanced transient response, and industry-pin-compatible upgrade path from legacy PFC controllers.

Technical Context

The UCC38051D operates in transition mode by self-oscillating: turn-on is triggered by zero-current detection at the ZCD pin, while turn-off is governed by the current-sense comparator comparing CS voltage to the multiplier output. Its transconductance error amplifier features dynamic slew-rate enhancement-activating >1 mA sink/source when VO_SNS deviates beyond 88% or 105% of VREF-to accelerate start-up and suppress output overshoot.

Key functional blocks include a 0.65 typ multiplier gain constant, 2.3-V zero-power comparator threshold on COMP, 0.23-V enable threshold on VO_SNS, and integrated overvoltage protection with 180-mV hysteresis referenced to VREF. The device supports two UVLO options: UCC38051D's narrow 2.8-V hysteresis enables downstream PWM coordination, unlike UCC38050's 6.3-V hysteresis optimized for standalone start-up.

Key Specifications

Pinout & Package

UCC38051D is housed in an 8-pin SOIC (D) package measuring 3.91 mm × 4.90 mm, with GND (Pin 6) as the thermal and signal reference plane. All bypass capacitors must connect to GND with minimal trace length.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar transition-mode PFC controller applications.

Compared with UCC38050D, UCC38051D trades higher UVLO threshold and stronger error amplifier drive for tighter system-level control integration; compared with UCC28051D, it offers cost-optimized commercial-temperature operation without sacrificing pin or functional compatibility.

Availability

UCC38051D is available at Aetrix Electronics and suitable for lighting ballasts, AC adapter front-ends, and set-top box power supplies requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production lots.

Supply support for UCC38051D includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in power management ICs and industrial-grade signal chain solutions.

The UCC38051D belongs to TI's UCC2805x/UCC3805x family of transition-mode PFC controllers, engineered specifically for cost-sensitive, low-to-medium power AC-DC conversion where IEC 61000-3-2 compliance and compact board area are primary design constraints.

FAQ

What is the UVLO behavior difference between UCC38051D and UCC38050D?

The UCC38051D has a 12.5-V UVLO turn-on threshold and 2.8-V hysteresis, enabling controlled activation by a downstream PWM controller in two-stage power supplies. In contrast, the UCC38050D uses a 15.8-V turn-on threshold and 6.3-V hysteresis for faster, autonomous start-up with smaller VCC capacitors. Both share identical pinout and core functionality, but their UVLO profiles define distinct system-level integration strategies - UCC38051D for coordinated control, UCC38050D for standalone operation. This difference is explicitly defined in the SLUS515G datasheet Section 6.5.

How does the zero-power detect feature protect the UCC38051D system during light-load conditions?

The UCC38051D monitors the COMP pin voltage and activates its zero-power detect comparator when COMP falls below 2.3 V. This condition occurs when output loading drops significantly, causing the error amplifier to reduce its output. Upon detection, the controller latches the DRV output low, halting switching and preventing uncontrolled output voltage rise. This mechanism avoids overvoltage stress on the boost capacitor and MOSFET without requiring external circuitry. The 2.3-V threshold is specified in the Electrical Characteristics table of the UCC38051D datasheet and is distinct from the 2.1-V threshold used in UCC2805x variants.

Can UCC38051D be used in a single-stage PFC flyback topology?

Yes, the UCC38051D is explicitly qualified for single-stage PFC flyback converters per its Applications section in SLUS515G. Its transition-mode control, integrated zero-current detection, and ability to regulate output voltage via VO_SNS feedback make it suitable for topologies combining PFC and isolation in one magnetic structure. Designers must ensure the flyback transformer auxiliary winding properly interfaces with the ZCD pin and that the CS pin senses primary-side current with appropriate scaling. TI provides reference designs (e.g., TIDA-01612) validating this use case with UCC38051D.

What is the role of the 75-mV offset in the MULTIN signal path of UCC38051D?

The UCC38051D applies a fixed 75-mV positive offset to the MULTIN input before multiplication. This offset compensates for zero-crossing distortion in the rectified AC line voltage, improving total harmonic distortion (THD) performance near voltage zero crossings. As confirmed in Section 7.3.6 of the datasheet, the offset shifts the effective multiplier input range upward, ensuring continuous current conduction and smoother input current waveform shaping - a critical factor for meeting IEC 61000-3-2 harmonic limits in lighting and adapter applications.

Does UCC38051D support overvoltage protection independent of the feedback loop?

Yes, the UCC38051D implements dual-stage overvoltage protection. First, slew-rate enhancement in the error amplifier pulls COMP below 2.5 V when VO_SNS exceeds ~105% of VREF, reducing multiplier output and limiting power delivery. Second, if VO_SNS rises above VREF + 0.18 V (2.68 V), the dedicated OVP comparator hard-latches DRV low regardless of COMP state. This secondary protection remains active even if the feedback loop fails or compensation components drift, ensuring robust safeguarding of the boost capacitor and switch. The OVP threshold and hysteresis are fully characterized in Section 6.5 of the UCC38051D datasheet.